This invention relates generally to a motion alarm system and particularly to a motion alarm system which provides an alarm if a motion detector does not provide a motion signal for a predetermined time.
In U.S. Pat. No. 4,205,300 there is described a vehicle anti-theft alarm system. The system includes a plurality of position sensitive switches for sensing motion of the vehicle. Each of said switches has an individual initial state dependent upon the position of the supporting surface for the vehicle and is arranged to change its state from its initial state in response to motion. The switches are respectively either opened or closed in their initial state depending upon the orientation of the vehicle surface and position of the switch. Some of said switches being open in the initial state and others being closed in the initial state. Switches individually selectively change from the initial state in response to movement of the vehicle. Circuit means are responsive to said switches individually being selectively changed from the initial state in response to movement of the vehicle for operating an inhibiting or alarm circuit.
The system is particularly advantageous because it does not require specific orientation of the motion detector. The motion detector can be mounted at any orientation and it is only movement which serves to provide a signal when one or more of the plurality of switches changes its state. Mercury switches disposed at different orientations in a switch assembly are described in one embodiment of the patent.
In many applications it is desirable to provide an alarm when motion ceases rather than when motion commences. One example is in fire fighting. The fireman enters a building or an area to combat fire. If the fireman is overcome by smoke or struck by falling debris, it is desirable to provide an alarm so that fellow firemen can come to his rescue. A system which could provide such an alarm would save lives. Generally under such circumstances the fireman is motionless. An alarm system which provides an alarm after the fireman is motionless for a predetermined period of time would alert his fellow firemen who would then come to his rescue. Other applications would be to alarm persons or things working or operating in a dangerous environment.